Mucin 1 downregulation decreases the anti-tumor effects of melanoma vaccine.

Abstract

Immunotherapy-based approaches are important breakthroughs with potential treatment benefits for melanoma patients. Mucin 1 (MUC1) is significantly upregulated in melanoma relative to normal cells. It has been reported that MUC1 influences cancer cell proliferation, apoptosis, invasion, and metastasis.The study aimed to explore the effect of MUC1 knockdown on the biological characteristics of the melanoma cell line B16F10 and evaluate whether MUC1 is an effective candidate target antigen for melanoma vaccine development. First, lentiviral vector-mediated short hairpin RNA (shRNA) was used to knockdown MUC1 in B16F10 cells (shMUC1-B16F10 cells). Next, we examined epithelial-mesenchymal transition (EMT), migration, proliferative capacity, clone formation, and distribution of cell cycle in shMUC1-B16F10 cells. Finally, the vaccine was prepared by repeated freeze-thawing of the shMUC1-B16F10 cells and used to subcutaneously immunize C57BL/6 mice, which were then challenged using B16F10 cells 10 days after the final vaccination. It was revealed that shMUC1 suppressed B16F10 proliferative and colony formation capacity, induced the arrest of cell cycle in the G0/G1 phase, and adjusted the expression of EMT-associated factors. MUC1 downregulation markedly suppressed the effect of B16F10 vaccine against melanoma in a mouse model. As compared with B16F10-vaccinated mice, B16F10-vaccinated mice in which MUC1 was silenced had reduced natural killer (NK) cytotoxicity, lower production of interferon-γ (IFN-γ), anti-MUC1 antibodies, perforin, granzyme B, and elevated tumor growth factor-β (TGF-β) level. MUC1 has strong melanoma vaccine immunogenicity, and induces the host's anti-tumor reaction. MUC1 knockdown inhibits the immune activity of B16F10 cell vaccine and anti-melanoma effect, suggesting the MUC1 is an important candidate target antigen of the melanoma vaccine.